In an example of conventional copier, shown for example in Japanese Patent Kokoku Publication 52378/1988, cut sheets on which a visible image is to be written are contained in a paper cassette and are picked up one by one by means of a pick-up roller and fed, via a conveyance path, to a writing section where a visible image is written by transferring a toner image from a photosensitive drum 41. A problem associated with the conventional copier is that a plurality of sheets, rather than just one, may accidentally be picked up simultaneously by the pick-up roller. This will result in a jamming in the conveyance path and the writing may be unsuccessful.
An object of the present invention to provide a copier in which jamming of sheets are prevented, and it is ensured that the writing on the sheets be successful even if a plurality of sheets are picked up by mistake, or otherwise supplied in superposition.
A copier according to the invention comprises:
a sheet supply means for supplying sheets in succession;
a writing section, where an image is written on the sheet;
characterized by further comprising:
a sheet separation mechanism disposed between the sheet supply means and the writing section to separate the sheets into ones when a plurality of sheets are supplied in superposition from the sheet supply means;
a sheet sensor producing a signal indicative of the passage of the sheet through a predetermined location between the sheet separation mechanism and the writing section; and
a control means for controlling the timing of the writing such that the initiation of the writing is in time with the arrival, at the writing section, of the leading end of the area of the sheet in which the image is to be written.
In the copier configured as described above, when a plurality of sheets are supplied in superposition, they are separated into individual sheets by the separation mechanism, and are sent out from the separation mechanism one after another. Moreover, the passage of each of the separated sheet sent out of the separation mechanism through a predetermined location upstream of the writing section is detected by the sensor, so the initiation of writing of image onto the sheet is in time with the arrival, at the writing section, of the leading end of the area of the sheet where the image is to be written, so the synchronization of the writing with the sheet feeding is ensured, even for the second and any subsequent superposed sheets which are simultaneously supplied and separated at the separation mechanism.